I so know this feeling. My two are always hungry and if it is a repeat of the day before they are so upset.
Fruit salad with yogurt
Vegetable stacks with a dip
Milkshakes/ smoothies
Pikelets
Muffins ( sweet and savoury)
Sausage rolls
Croquettes
Tuna patties
Nachos
Crepes
Taco/tortillas

I like to snack on dried apricots. The sweetness should satisfy your kids and make for a yummy snack. You could also chop them up and mix with some condensed milk and coconut to make apricot balls. They’re nice and easy to make and hopefully a hit with your kids.
Good luck in the coming weeks :-)